Mixing of granular material with liquids



July 2,

Filed Nov. 7, 1945 3 Sheets-Sheet 1 INVazvfaR M MM July 2, 150 L. WALKER HIKING 0F GRAWLAR MATERIAL WITH LIQUIDS 3 Sheets-Sheet 2 Filed Nov. 7, 1945 HGA.

INVzNTbR L. WALKER 2,516,436

HIKING OF MATERIAL II'I'HLIQUIDS 3 Sheets-Sheet 3 25, 1. Filedflov. 7; 1945 Patented July 25, 1950 mxmGor-cmumnmmmwrm nnzmms- Lionel Walker, Sheflield, England Application November 7, 1945, Serial no, 627,258 v In Great Britain November 28, 1944 a s Qlaima.

This invention relates to the mixing of granular material with liquids, its object being to provide an improved process and apparatus for producing an intimate mixture resulting in a plastic product. The invention is particularly applicable to the mixing of clay with water in the manufacture of bricks, tiles, stoneware, and other ceramic products.

According to the present invention, the relatively dry granular material is brought into contact with a liquid while'under reduced pressure so as to remove the greater portion of'the air from the neighbourhood of the material, and thereby facilitatethe entrance of the liquid into the pores or cells of the material. The pressure is preferably in the neighbourhood of 2 lbs. per square inch absolute or less. Small volumes of air contained in pores or cells of the grains of material may thus be removed, and the intimacy of the mixture increased.

Preferably the grains of material are subjected to the reduced pressure of the vacuum chamber before they come into contact with the liquid. The liquid is preferably distributed by spraying.

Pressure may be applied to the discrete grains of material in the presence of the liquid before agglomeration has taken place to assist the entrance of the liquid into the evacuated pores and cells. Such pressure may be applied pneumatically by allowing the pressure in the vacuum chamber to rise by admission of a preferably controlled quantity of air, before the mixture has conglomerated into a mass of such density as to remove the particles from contact with free or mobile liquid.

It is convenient to efiect such a rise in pressure by permitting communication between thechamber at the reduced atmospheric pressure thereof.

The temperature at which the process is carried out may be raised above that normally pre- 2 veiling, especially in winter and cold periods; thus the liquid may beheated.

The appliedmechanical pressure may operate to carry the mixing of the wetted material to an intimate degree and bring. the mass into suitable compacted condition for its ultimate use, e. g. making into bricks.

Although the intimate mixing that may be carried out while the materials remain under reduced pressure enables a highly homogeneous product to be directly obtained, the primary advantage of the invention is that it enables the production of a plastic mass from predetermined amounts of granular material and liquid in which thewetting liquid is substantially uniformly distributed throughout the mass. This result arises because each quantity of granular material is thoroughly permeated by each delivery of liquid. A substantially uniform mass may, therefore, be produced without any mechanical mixing taking place under reduced pressure; intimate mixing may, however, be carried out after the wetted material has been removed from the reduced pressure conditions in which the granular material and the liquid have been brought together.

Apparatus according to the present invention comprises a. vacuum chamber, means for exhausting air therefrom, a feed inlet thereto controlled by a valve adapted to admit granular material to the chamber and to seal the inlet, means for spraying liquid inside the chamber, and a discharge outlet.

Although the discharge outlet may be controlled by a valve, it is preferably sealed by an accumulation of the plastic product resulting from the mixture of granular material and liquid inside the chamber. To start the apparatus, a sealing plug of plastic material must first be pressed into the outlet.

Rollers may be mounted insidethe chamber adjacent the outlet and may be driven from the exterior to apply pressure to material between them and to extrude such material through the outlet.

Again, an extrusion screw may be provided to compact the mass andv to press it through the outlet.

The mechanical pressing means may, however, be separate from the discharging means. Thus,

3 of the vacuum chamber, the liquid spraying device at a lower level, the pressing means (if provided) still lower, and the discharge outlet at the base An exhaust pump is connected-to the chamber at any convenient position, the inlet to such connection being preferably shielded by illtering material The valve controlling the feed inlet may be of a rotary, reciprocating. or other type. It may be arranged to permit the admission of air through the bulk material at each delivery in cases where it is desired to raise the pressure in the vacuum.

chamber to assist the entrance of the liquid into the evacuated pores or cells; such a valve allows the vacuum to pull on the bulk material and aslist in the delivery of substantially uniform amounts of material.

Various forms and arrangements of apparatus according to the invention are shown in the accompanying drawings, in which Figure l is a diagrammatic elevation, partly in section, of one arrangement;

Figure 2 is a side elevation in section of part of Figure 1;

Figure 3 is a sectional plan taken on the line 3-3 of Figure 1;

Figures 4 and 5 are front and side elevations, partly in section of another arrangement;

Figure 6 is a modification of Figure 4; and

Figure l is a more detailed vertical section of another modification.

Like reference numerals indicate like parts throughout the drawings.

Referring to Figures 1 and 2, a vacuum chamher I is disposed below a hopper 2 for granular material, (hereinafter referred to as "clay) a rotary valve I with pockets 4 providing for the delivery to the chamber of predetermined Amounts of clay at a rate determined by the drive -from any source of power (not shown) through the reduction gear 5. Below the valve 3 is a nozzle 0 supplied with liquid (hereinafter referred to as "water) through a valve 1 of the poppet type,

' opened by engagement between a mushroom head 8 on the valve and a cam I also driven by the gear 5. The nozzle t points downwardly to the vacuum chamber I, so as to spray with water the clay dropped into the chamber from the pockets in the valve 3. The pocketed valve seals the vacuum chamber and enables a substantially uniform pressure to be maintained therein during and between the delivery periods.

The spraying periods may either coincide with or alternate with the delivery periods of the granular material.

An outlet II of the chamber I connects the chamber to a vacuum pump I I through the jacket I! communicating at its bottom with the chamber. The jacket may contain scrubbing material such as steel wool. The outlet connection delivers the exhausted air to a washer It in which a rose ll discharges below the level of liquid I5 to remove as much as possible of any material entrained by the air. A baiiie II! above the level of the liquid helps to remove moisture picked up by the air, and the air passes through a line filter It before reaching the vacuum pump II to protect the pump against wear.

Below the vacuum chamber I is a receiver I'I provided with a bottom discharge outlet it towards and through which the mixture of predetermined amounts of clay and water is propelled by one or more curved arms I! (Fig. 3) mounted on a vertical shaft 2| passing through a gland 2! 4 in the bottom of the receiver. The shaft It is driven through reduction searing 22.

A plug of clay seals the outlet II and so enables the desired low pressure to be maintained in the chamber I and receiver I'I. Initially, an already prepared plug should be placed in the outlet to enable the vacuum pressure to the working level.

The shaft 20 may carry mixing arms 23 of slight pitch that operate to apply pressure to the clay in the receiver I1 and assist the penetration of the evacuated pores and cells of the clay by the water. Alternatively or in addition, the mechanical mixin following the spraying of the clay may be carried out outside the vacuum chamber and receiver in any suitable type of mixer.

. Figures 4 and 5 show the vacuum chamber I connected to the hopper 2 by a rotary valve 24 of the plug type with a transverse passage 28' through which the clay falls as the rotation brings it into registration with the hopper twice in'every revolution. The reduced pressure in the vacuum chamber aids the passage of the clay. At each delivery period, air is admitted through the bulk material in the hopper and raises the internal pressure of the vacuum chamber to apply pressure in the presence of the water to the already evacuated discrete grains previously delivered to the vacuum chamber.

Figures 4 and 5 also show the receiver of Figure 1 replaced by an enlarged portion 28 housing a pair of rollers 21 with a gap 28 of desired width between them and extending across the whole width of the portion 26 to apply pressure to the wetted clay and discharge it as a plug through the tapered extension 29 to the outlet opening 8.

Figure 6 shows. a vacuum chamber similar to that of Figure 4 with an extrusion screw it for pressing the material and discharging it to the opening 8.

In Figures 4 to 6, the outlet is to the vacuum pump is connected to an annular space II surrounding the bottom of the vacuum chamber I and connected to it through the perforated skirt A modified form of valve is shown in Figure 7. The shaft 33 carrying the cam 9 for operating the water valve 1 is extended into the passage 3! connecting the vacuum chamber I to the hopper 2 and carries a cam 35 that engages the bottom of the stem 36 of a valve 31 projecting into the bottom of the hopper. The underside of the valve is faced with rubber 38 to engage a metal seat 39. when the valve is lifted, material can pass from the hopper into the chamber I, aided by the reduced pressure in the chamber. As with the valve of Figures 4 and 5, this type of valve permits the entry of a limited amount of air through the bulk material to raise the pressurein the vacuum chamber, and also to assist in pulling the charge into the chamber.

' What I claim is:

1. A process for the production of plastic material comprising introducing dry granular material into the upper portion of a, zoneot reduced pressure, thereby causing the material to fall pump to reduce the becsire said material settles or partially agglomera 2. A process for the production of plastic material which comprises introducing intermittently dry granular material into the upper portion of a zone of reduced pressure, thereby causing said material to pass through said zone, intermixing a liquid with said material in scattered form in said zone by simultaneously spraying said liquid into said zone in predetermined amount in relation to said granular material.

3. A process for the production of plastic material which comprises introducing dry granular material into the upper portion of a zone of reduced pressure, thereby causing said material to pass through said zone, intermixing a liquid with said material passing through said zone by simultaneously spraying said liquid into said zone in predetermined amount in relation to said granular material, and mixing the resultant agglomeration of granular material and liquid into a homogeneous plastic mass.

4. A process for the production of plastic material which comprises introducing dry granular material into the upper portion of a zone of reduced pressure, thereby causing said material to pass through said zone, intermixing a liquid with saidmaterial passing through said zone by simultaneously spraying said liquidinto said zone in predetermined amount in relation to said granular material and thereafter increasing the pressure in said zone to aid agglomeration of said liquid and material.

5. A process for the production of plastic clay comprising introducing dry granular clay into the upper portion of a zone of reduced pressure. thereby causing the clay to fall through said zone, intermixing a liquid with said'granular clay during its fall through said zone by simultaneously spraying said liquid into said zone in predetermined amount in relation to said clay, and

conducting said inter-mixing at a temperaturev above ambient temperatures, whereby in the substantialabsence of air the liquid enters the pores of the granular clay and intermixing is complete before said clay settles or partially agglomerates.

6. Apparatus for the production of plastic material, said apparatus comprising a vacuum chamber, means for exhausting air therefrom, a valve-controlled feed inlet in the upper portion of the chamber for the admission of relatively dry granular material to the chamber, a liquid spraying device at an immediately lower level than, and vertically beneath, the said feed inlet, and an outlet in the lower portion of the chamber for the removal of the plastic mass resulting from the wetting of the granular material.

7. Apparatus for the production of plastic material, said apparatus comprising a vacuum chamber, means for exhausting air therefrom, a valve-controlled feed inlet in the upper portion of the chamber for the admission of relatively dry granular material to the chamber. a liquid spraying device at an immediately lower level than, and vertically beneath, the feed inlet, means for applying mechanical pressure to the wetted material at a still lower level, and an outlet in the lower portion of the chamber for the removal of the plastic mass resulting from the wetting of the granular material.

8. A process for the production of plastic material comprising the steps of passing a dry granular material through a zone of reduced pressure, intermixing a liquid with said material passing through said zone by simultaneously spraying said liquid into said zone in predetermined amount in relation to said granular material.

LIONEL WALKER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

